The present invention relates to a self-protective high-current low-loss bi-directional semiconductor switch device and method of operation. More specifically, the present invention focuses on a bi-directional semiconductor switch module capable of controlling the magnitude and direction of an energy flow, for instance electrical current, between a first and a second terminal of the bi-directional switch module in response to a measured value of the energy flow and a default value, and wherein the default value could be replaced by an input value received via a receiver included in the bi-directional switch module. The device is constructed such that high-current, typically from 100 to 1000 amperes can be accommodated, making it ideal for applications in vehicle electrical systems.
Electrical systems comprising bi-functional devices where each device can operate either as a load or a source require a bi-directional switch so that electrical energy can be exchanged between the devices according to the system operating conditions. For instance, a vehicle electrical system generally comprises a battery and an alternator where each device can operate either as a load or a source. Whenever the alternator is not operating, including the engine start process, the battery provides electrical energy to the vehicle electrical system. When the battery is the source of electrical energy it is desirable to have a switch monitor and limit the battery discharge energy, and to disconnect the battery from the electrical system if needed. The alternator functions as a source of electrical energy after it attains a certain RPM, at which point the battery is recharged by the alternator. When the alternator is the source of electrical energy, it is desirable to have a switch monitor and limit the alternator power to the battery and the electrical system, and to disconnect the battery from the electrical system if the battery recharge current demand causes the alternator capacity to be exceeded. It is also desirable that the switch can detect a short circuit current in either direction and disconnect the energy source from the short circuit. Therefore, a bi-directional switch module is needed that can control the magnitude and direction of electrical current by controllably switch on/off said electrical current in either direction between two such bi-functional devices.
Vehicle electrical systems comprising multiple systems of batteries require controlled electrical energy exchange between the batteries. For instance, a vehicle electrical system utilizing a main and an auxiliary system of batteries requires controllable switching of electrical current between the battery systems according to the vehicle operating conditions. The main system is used during startup and whenever the alternator is not operating, and the auxiliary system is used when the vehicle engine is not operating. The main and auxiliary systems are connected in a parallel configuration and require a switchable means between them to control the exchange of electrical energy in both directions according to the vehicle operating conditions.
In the event that the main system is depleted or otherwise defective, the auxiliary system can transfer electrical energy to the main system. Similarly, if the auxiliary system has exhausted its energy and there still remains a critical need to provide electrical energy to the electrical loads, the main system can transfer electrical energy to the auxiliary system. However, a transfer of electrical energy between these systems based solely on the amount of energy stored within these systems is undesirable. In a situation where the main system's electrical energy is needed for vehicle startup, it is detrimental to allow the system to supply electrical energy to a depleted auxiliary system. Similarly, when there is a critical need for the auxiliary system to provide electrical energy to an auxiliary load, it is undesirable to allow the auxiliary system to supply electrical energy to a depleted main system. A bi-directional switch module that can receive input values for controlling the magnitude and direction of electrical energy exchange according to the vehicle operating condition is preferred.
Although various devices have been proposed that address some aspects of the present invention, no single device has been constructed which provides controlled switching of high electrical currents in either direction between two bi-functional devices. For example, Rumennik, U.S. Pat. No. 5,323,044 discloses a novel way of constructing bi-directional switches utilizing MOSFETS, but does not address controlling the magnitude and direction of electrical current between such MOSFETS. In Kinzer, U.S. Pat. No. 4,755,697, the invention focuses on a high voltage bi-directional output semiconductor field effect transistor that operates at high voltages and replaces electromechanical reed relays. The present invention controls high electrical currents in the 100-1000 amperes. The Juzswik patent, U.S. Pat. No. 5,210,475 discloses a current sensing circuit utilizing MOSFETS for detecting over-current condition in “H-bridge-type” power delivery circuits for bi-directional motors, but it does not address controlled switching of high electrical currents. Consequently, there is a need for a bi-directional switch module that can control the magnitude and direction of large electrical currents between a first and second terminal of such switch module.
Modern vehicle electrical systems utilize bi-functional devices that demand large electrical currents. Furthermore, electrical energy exchange between these devices must be controlled, not simply based on the available energy, but also the operating condition of the vehicle. Various vehicle operating conditions affect the function of each device that make up the vehicle electrical system. For instance, in a vehicle electrical system comprising a battery and an alternator, the battery operates as an electrical energy source during the vehicle start process and subsequently becomes an electrical load when the vehicle is operating. The alternator is an electrical energy load during the start process and operates as an electrical energy source while the vehicle engine is operating. Such devices require a bi-directional switch module that can control the magnitude and direction of large electrical energy between said devices while protecting the electrical system.